Nanomaterials have generated unprecedented interest due to their unusual physical and chemical properties with wide and divergent applications in optics, electronics, magnetics, mechanics and catalysis. Nanocrystalline metal oxides exhibit unparalleled destructive adsorption properties of acid gases, polar organics, and even chemical/biological warfare agents. Due to high surface area, these nanostructured solid materials display good catalytic activity in isomerisation, alkylation, reforming and dehydrohalogenation reactions.
Generally, aerogel samples are prepared by supercritical drying of a gel from a sol-gel reaction. The aerogel has a specific high surface area with low density. Due to its physical characteristics, aerogel sample is useful as a catalyst or as a carrier for a catalyst.
LDHs (layered double hydroxides), which consist of alternating cationic MII1-x-MIIIx (OH)2x+ and anionic An−.zH2O layers have received much attention in recent times in view of their potential applications as catalysts, adsorbents, biomaterials for controlled drug delivery and gene reservoirs.
Reference is made to Nanostructured Materials. 1999, 11, 1091 wherein nano particles of Zinc oxide and alumina were prepared independently by chemical arrested precipitation and then converted into nanocomposites by wet mixing. The inherent disadvantage of this protocol is the development of non-homogeneous material.
Reference is made to Journal of Solid State Chemistry, 2002, 165, 193 wherein binary oxides like titanium dioxide and tin oxide are prepared by stearic acid method wherein particle size range from 10-15 nanometers. The drawback is the system is non-homogeneous.
Reference is made to Chemistry of Materials, 2002, 14, 2922 wherein binary alumina and magnesium oxides were prepared by sol-gel method. The ratios of the alumina and magnesium oxides were not related to the normal hydrotalcites. The drawback is the system is non-homogeneous.
Reference is made to Nature, 2000, 403, 65 wherein the homogeneous nanobinary barium oxide and alumina were synthesized by reverse microemulsion technique. The particle size ranges from 3-10 nanometers. The drawback is use of expensive protocol.
Reference is made to Microporous and Mesoporous Materials, 2000, 39, 229 wherein the nano layered double hydroxides were prepared by sol-gel method. The drawbacks are the size of the particles are high, ranging from 300-600 nanometers and the surface area of the samples lower ranging from 240-270 m2/g.
Reference is made to Chemistry of Materials, 2002, 14, 4286 wherein nano-layered double hydroxides with uniform crystal size were prepared by co-precipitation in colloid mill and aging for 100° C. for 13 h. The drawback is that the particle size obtained in this method is about 60-80 nanometers.
Reference is made to Journal of American Chemical Society, 2000, 122, 3530 wherein the zeolite nanoparticles assembles into thin films, membranes, or fibers.
Reference is also made to Akgewandte Chemie, 2002, 41, 1188 wherein the quasi-spherical zinc oxide nanoparticles assemble into nanorods.